Tag: Series

Despite a recent resurgence in popularity, oval chainrings are not new technology. Dating as far back as 1890, non-round chainrings have made numerous appearances in the marketplace, with the most in/famous being Shimano’s Biopace. More recently, oval rings enjoyed a boost in popularity when professional road racers Chris Froome and Sir Bradley Wiggins used non-round rings in their quests for Tour de France victories. And now, oval chainrings such as those offered by absoluteBLACK are seeing more use among off-road riders.

You’ve read GRAVELBIKE’s series of articles on 650B conversions, and now you’re thinking about converting one of your own bikes. While the process is relatively simple, every bike (and setup) is a little different, and there’s always the possibility of a gotcha lurking in the shadows. After spending countless hours testing various wheels, tires, and other components, we’ve compiled a list of tricks, tips, and lessons learned that’ll make your 650B conversion that much easier.

Mind The Gap
Tire casings relax and typically plump up a few millimeters after being inflated for 24-48 hours. Check your tires’ clearance a day or two after the initial installation to confirm that there is still adequate clearance at the frame, fork, or fenders. When in doubt, opt for a narrower tire, especially if you’ll be riding in muddy or snowy conditions.

Keep It Simple
If you plan on swapping wheels for different terrain or conditions, try to use the same components on both wheels. Having to adjust brake calipers or rear derailleurs every time you change wheels can be time consuming and frustrating. Sure, practice can make the task easier, but when both wheelsets have the same hubs, cassettes, and rotors, you can spend more time riding.

Know Thy Limits
Fat tires and low gears can take you to some exciting new places. If you haven’t ridden a particular bike off-road prior to the 650B conversion, take it easy until you’re comfortable with the new wheels’ effect on handling and braking (both on- and off-pavement). This is especially important if the different wheels change the bike’s bottom bracket height or steering geometry.

In this series’ previous installment, we covered the wheels-and-tires portion of GRAVELBIKE’s Salsa Vaya 650B conversion. For this entry, we’re going to spend some time talking about gearing.

Salsa has always spec’d the Vaya completes with sensible gearing, and my own Vaya’s gearing (36/46, 11-34) was more than adequate for pavement and gravel. For extended climbs on rocky terrain, however, that gearing simply wasn’t low enough. Drawing on my past experience with 26″-wheeled bikes, I knew that a sub-1:1 low gear would not go unused when exploring more rugged trails.

Achieving that low gear turned out to be a bit of a challenge due to the fact I was running such an eclectic mix of drivetrain components (10s Campagnolo shifters, 9s daVinci/SRAM rear derailleur, Shimano 9s cassette). Taking inspiration from Salsa’s Fargo off-road adventure bikes, I decided that a mountain-double crank would give me the low gear that I needed without having to replace any other components.

To maintain compatibility–and eek out every last bit of shifting performance–many crank manufacturers offer dedicated chainring combinations designed to work specifically with Shimano or SRAM systems. Since my hodgepodge setup contained a mix of both companies’ components, I needed a crankset that would play nicely with a non-dedicated setup. Thankfully, Full Speed Ahead designed their Afterburner double crankset to be compatible with both Shimano and SRAM drivetrains.

Installing the Afterburner crankset was a breeze, requiring only a 5mm hex key and Shimano Hollowtech II-compatible socket. During my testing, I alternated between 24/38 and 22/36 chainring setups, logging the most miles on the 22/36 combo. While it wasn’t designed for such tiny chainrings, the Campagnolo Veloce front derailleur shifted better than expected when it was positioned such that it barely cleared the chainstay.

On paved and gravel roads, the 36t chainring proved surprisingly versatile. There were a few situations where I found myself wishing for a taller top-end, but I never felt handicapped by the 36/11 high gear. When it came to navigating steep, rocky trails, the 22t chainring was invaluable. I could cruise along in the 36t ring, drop down to the 22t when the trail started to get steep, and then fine tune my cadence by shifting up or down the cassette. Thanks to the added height of the 650B knobby tires, pedal strike wasn’t an issue with the 170mm cranks when traversing rock gardens or navigating stair-type obstacles.

If you tend to divide your riding equally between pavement and dirt, consider a mountain-double crankset. For riders seeking a wider gearing range–while still maintaining the simplicity of a double-chainring system–Full Speed Ahead offers the Afterburner in 26/39 and 42/28 combinations.

Disclosure: Full Speed Ahead provided product samples for this article, but offered no other form of compensation for this review.

Welcome to the second installment of GRAVELBIKE’s series on converting the Salsa Vaya to 650B wheels. Previously, we covered the why, and in this post, we’ll explain the how.

If you’re wondering why someone would go to the trouble of converting a bike like the Salsa Vaya to 650B/27.5″ wheels, the answer is volume. Specifically, air volume. A 650B/27.5″ knobby has the same outside diameter as a 700×38 cross or touring tire. The 650B rim, however, is smaller than a 700C rim, giving you more tire height (or volume). That added height/volume allows you to run lower air pressure (with reduced risk of pinch-flatting), which smooths out the ride and improves traction when riding off-road.

Both tires have a diameter of 705mm, but the 650B tire (right) has 45% more height than the 700C tire (left).

Thanks to the growing popularity of 27.5″ tires in the MTB world, nearly every manufacturer offers compatible wheels and rims. For this project, we selected Bicycle Wheel Warehouse’s 650B Pure Enduro Pro wheelset. The 26mm wide rim can easily accommodate 2.5″ wide tires, yet weighs only 420g. With the company’s PURE-branded D400 hubs (32h) and Sapim CX-Ray spokes, the Enduro Pro wheels came in at 731g front and 831g rear. We used inner tubes during the majority of the testing, but had no trouble running Hutchinson Cobra tires without tubes (using Stan’s rim strips and Slime tubeless sealant). During the test period (several weeks of daily riding), the only necessary maintenance was tightening the rear hub’s end-caps after the initial break-in period. Both hubs’ seals proved effective at keeping out water and dirt, despite being ridden in record-breaking rainstorms.

Bicycle Wheel Warehouse PURE D400 front hub.

When retrofitting a 700C- or 26″-wheeled bike with 650B wheels, be aware that not all 650B/27.5″ knobbies will fit. In the case of the Vaya, lateral clearance was more of an issue than vertical clearance. Keep in mind that tires often measure-out differently than their stated size. Actual dimensions can vary by manufacturer, and in some cases, even between different models from a single company. Another factor to consider is rim width. Wider rims can change a tire’s profile, increasing the effective size (thereby reducing clearance). Lastly, it’s not uncommon for tire casings to relax (or stretch) after they’ve been mounted and inflated (every tire that we tested measured 1-3mm wider 24-48 hours after installation).

Tires are listed alphabetically by name, and include the inch-based and metric sizes as per the manufacturer. Note that there is no winner because we didn’t view the project as a contest. Each tire performed well, and had its own strengths and weaknesses. Tire preference–like many choices in cycling–is often subjective at best. The ratings (1-5, with 5 being the best) are relative to the other tires tested. A tire that received a 5/5 pavement rating would be smoother-riding than a tire that received a 3/5 rating, but that 5/5 tire won’t be faster on-road than a 25mm tubular. Tires were evaluated by the following criteria: